In the conveying of various materials and in the conveyors constructed therefore, the most vulnerable device in the conveyor is the flight attachment. If a foreign object is lodged in the conveyor in such a way that it is placed in the path of a flight, it would be possible for the conveyor to continue to run and damage all the flights on the conveying chain. Additionally, if a foreign object is carried into the head sprocket or driving sprocket of the conveyor, it could break the chain, throw it off the sprocket, or break the sprocket.
Several methods have been utilized in the past to detect these problems. These methods have met with minimal, if any, success. Some of these previous methods include zero speed detectors, motor load detectors, and proximity detectors.
A zero speed detector requires a device located on the tail or idler sprocket that will respond to a condition wherein the sprocket shaft has stopped revolving. If the flights or material carrying devices of the conveyor are being damaged and the chain continues to run without a break, this type of speed detector will not reveal such a problem. Further, if there is a chain break just behind the drive sprocket on the slack side, the tail sprocket will continue to revolve while the possibility of chain accumulation or "snow balling" around the drive sprocket exists.
The ineffectiveness of a load detector on the drive can be easily realized when one considers the varying loads presented to the drive during normal operation. A conveyor may be empty, partially full, or completely full at any time, thus requiring chain pull over a wide range. If a foreign object were situated in the conveyor, the flights could be damaged and the load detector would only consider this to be a normal loading.
Proximity detectors have problems similar to the zero speed detector in that damage may occur many feet before it becomes apparent to the detector device.
With applicant's device all of these various problems are overcome.
With applicant's safety device, a certain degree of latitude is provided for initial take-up and tensioning of the chain being utilized. Past the degree of this adjustment situation, the detector and switching control mechanism will come into operation such that should the tail sprocket be moved forwardly the detector will activate the switch to de-energize the driving portion of the conveyor and likewise, should the chain break, and the tail sprocket, being spring loaded, be moved rearwardly, the detector will, through the switch de-energize the driving portion.
It is therefore an object of applicant's invention to provide a detector unit for use with conveyor devices which will sense the load being placed upon an idler or tail sprocket of the conveyor and will control the driving portion of the conveyor in response to movement of the idler sprocket.
It is a further object of applicant's invention to provide a conveyor safety mechanism which includes means for mounting an idler sprocket of the conveyor with means for permitting limited movement of the idler sprocket before actuation of a detection unit which detection unit is arranged to control the drive mechanism of the conveyor such that the drive mechanism of the conveyor will be de-energized on a pre-determined movement of the idler sprocket portion.
It is still a further object of applicant's invention to provide a safety detection device for a conveyor system wherein the detection device will provide a means to determine any abnormal load upon the flights of the conveyor or will determine chain breakage of the conveyor and will thereupon de-energize the driving portion of the conveyor.
It is still a further object of applicant's invention to provide a safety detection device for a conveyor mechanism which includes a first positioning arrangement for an idler or tail sprocket of a conveyor and which will provide a pre-load arrangement for the conveyor structure which will normally control the drive portion of the conveyor over a proper and normal driving load for the same.